System for storage and utilization of fuel gases



June 13, 1944. A. N. KERR j 2,351,131

SISTEM FOR STORAGE AND UTILIZATION OF FUEL GASES Filed Nov. 28, 1940 INVENTOR A.N. KERR 1 g I 'BY f v I M, I v ATro ngY Pmnaa June 13, 1944 SYSTEM FOR STORAGE AND UTILIZATION OF FUEL GASES Arthur N. Kerr. Los Angeles, Calif assig'nor to Phillips Petroleum Company, a corporation of Delaware Application November as. 1940, Serial No. 361.647

4 Claims.

Jhis invention relates to a system for the stor age and utilization of fuel gas.

More particularly this invention relates to a system for the storage of volatile liquids and liquefied gases and for vaporizing and dispensing them as gases.

Liquefied petroleum gases, chiefly propane, butane, and mixtures of the two are being marketed extensively for use as gaseous fuels in communities where manufactured or natural gas is not available. In utilizing these fuels, it is necessary to change them from liquid to gas and in most instances to make a reduction in their pressure. The liquefied fuel may be converted to a gaseous fuel in either of two ways. Gas may be withdrawn from the storage container in which event the .vaporization takes place in the container, or liquid may be withdrawn from the .storage container and gasified in an external vaporizer. The former method is known as batch" vaporization or simple distillation; the latter is known as flash" vaporization.

Many liquefied gas dispensing systems are operated with batch vaporization taking place in the storage container. In these systems the gas is withdrawn from the vapor space of the container, the latent heat of vaporization being supplied by the liquids and the container surroundings. When a mixture of liquefied gases, such as a propane-butane mixture, is difierentialiy distilled, the composition of the gas obtained initially is different from that obtained as the withdrawal continues. The composition and other properties of the gas withdrawn change continuously during the vaporization. At the same time the boiling point of the liquid remaining in the container changes as the gas is withdrawn. The initial boiling point of the liquid corresponds to the boiling point of the mixture whereas the final boiling point approximates that of the highest boiling component in the mixture. The final boiling point of most mixtures of propane and butane marketed as liquefled fuel gas is about 35 F. The initial boiling points of these mixtures is sometimes as low as '10 F. It is evident that for satisfactory service with the systems employing batch vaporization, the storage containers must be maintained at temperatures above the final boiling point or above 34 F. for a propane-butane mixture.

The system of the present invention utilizes flash vaporization. This type of vaporization results in a gas of uniform composition. Variations in important properties, namely, thermal value, specific gravity, and dewpoint of the vapors,

which are inherent in systems employing batch vaporization, are thus avoided. Liquid may be withdrawn from the storage container under its own pressure at any temperature above the initial boiling point of the liquid. Thus the storage tank may be set above ground where the atmospheric temperature is not lower than the initial boiling point of the mixture.

An object of this invention is to provide an improved system for the storage and utilization of fuel gases.

A further object of this invention is to provide a system for dispensing volatile liquids and liquefied gases in which the thermal value of the gas dispensed is substantially constant.

A still further object of this invention is to provide a system for dispensing and vaporizing liquefied gases and volatile liquids in which any condensate or unvaporized liquid is vaporized before entering the customer's service pipe.

Another object of this invention is to provide a gas dispensing system by which atmospheric heat exchange may be supplemented to insure vaporization and an adequate supply of gas.

Other objects and advantages will be apparent from the description and the accompanying drawing which is a diagrammatic elevation view of apparatus suitable for accompishing the objects of this invention. I

The present invention as described hereinafter and illustrated in the accompanying drawing is especially suitable for use in mild climates, such '8.8 the southern part of the United States, where there are relatively few cold days each year.

It will be apparent to one skilled in the art that the system herein disclosed may be readily adapted for use in colder climates. The invention aims to employ atmospheric heat for the purpose of supplying at least a part ofthe latent heat of vaporization while the balance of the heat necessary for vaporization is supplied by suitable heat exchangers and a carbureting tank.

With reference to the drawing, the numeral designates-a storagetank which may be located either above ground or buried in the earth. The choice of the location of the tank will depend upon the fuel used, statutory regulations, and other conditions. From the standpoint of operation, it is only necessary that the temperature of the container be maintained above the initial boiling point of the liquid stored therein. Liquid is withdrawn from the storage container through the valve 2 and pipe late a liquid regulating valve 4. The liquid regulating valve 4 is of conventional construction and is so constructpart or all of the heat vaporization is supp to the liquid. On a warm day, when the atmospheric temperature is higher than the tidal boiling point of the liquid. all of the latent heat of vaporization may be supplied to the liquid by at-' mospheric heat exchange in the air coil. Vapor and unvaporized liquid from the air coil pass through the valve I to the underground pipe 8. The underground pipe 8 provides heat exchange between the fluid passing through it and the surrounding earth. This fluid is passed through the valve 9 to the carbureting tank l0. Arranged within the bottom portion of the tank I0 is a pipe ll having perforations it through which the fluid entering the carbureting tank must pass. If any of the fluid entering the carbureting tank is in the liquid phase, it is retained by the action of gravity until it is vaporized. Gas from the carburetor l0 passes through the gas pressure regulator it, which reduces the pressure of the gas to the final desired pressure, and into the customers service line H.

The carbureting tank It provides heat exn e between the fluid therein and the surroundingearth. Liquid tendingtocollect in the carbureting tank is subject to vaporization by the combined action of heat from the earth and the stripping effect of the gases passing through the pipe II and the perforations l2. Thus any condensate or unvaporized liquid resulting. from a period of cold weather is collected in the carbureting tank and vaporized during warm weather. :It the air coil 8, piping 8, and carburetor I 0 do not supply sufllcient heat to completely vaporize the liquid withdrawn from the storage tank, the least volatile portion of the liq id will tend to collect in the carburetor. Ordinarily this will take place only during short periods of time. In case of an unusually cold period or an unusually long period of cold weather or a large demand for gas during cold weather, the carburetor may become nearly filled with liquid. ,To vaporize this liquid and increase the capacity of the system during such cold periods, the auxiliary vaporizer II may be used.

The auxiliary vaporizer ll comprises a coil I I or heating surface to which heat may be supplied by the burner l1. Fuel for the burner I1 is withdrawn from the customer's service line it through the valve i8 and pipe I9. When the auxiliary vaporizer I6 is put into service the valve 9 is closed or partly closed and the valves 20, 2| are opened. Fluid from the pipe 8 then flows through the valve and pipe 22 to the coil I! Where it is gasifled. Heated gas from the 'vaporizer flows through the valve 2| into the pipe I i and through the perforations l2 into thecarburetor it. The heat and the stripping action oi the heated gas serves to vaporize any liquid which has accumulated in the carburetor.

If it is desired to operate the system without the use of the air coil 8, the liquid from the liquid regulating valve 4 may be passed through the valve 23 into the pipe 8.

For the purpose of illustration, it will be assumed that a mixture of 40% propane and 60% normal butane is to be dispensed on a day when the atmospheric temperature is 20 F. The boiling points of such a mixture under a pressure or 8 ounces per square inch gauge are approximately as follows.

Liquid Boiling evaporated point Percent Degree: F.

0 l0. 0 l0 7. 5 20 4. 6 30 0.0 40 7. 5 b0 10. 5 60 17. 6 63 $10 70 25. 0 30. 0 35. 0 37. 5

From the foregoing table it is seen that at 20 F. and 6 ounces Der square inch pressure, 37% of the liquid is not evaporated. The conventional dispensing system operating on the batch vaporization principle would cease to supp y gas when 63% oi the mixture were withdrawn as gas from an above ground, unheated, storage container. Thus more than one third of the liquid could not be removed from the storage tank as a gas under a pressure of '6 ounces per square inch gauge without supplying heat to the storage container. This pressure is chosen as that necessary to insure satisfactory gas service. The storage container of some systems operating on batch vaporization are under ground and often below the frost line. of the earth is warmer than the atmospheric temperature during cold weather. these installatlon will supply gas until the temperature of the storage container is approximately equal to the temperature of the surrounding earth. The evaporation of the liquid from the storage container removes heat from the surrounding earth and lowers its temperature. During cold periods or periods of heavy gas withdrawals the temperature of the earth may be lowered below the boiling point of the liquid remaining in the storage tank and cause an interruption in the gas service.

The present invention will operate to utilize exchange with the earth in the pipe 8 and carburetor ill, or by the auxiliary vaporizer Ii. In the present example 63% 01 the mixture may be vaporized in the air coil at 20 F. leaving only 37% to be vaporized by the heat of the earth. It is evident that this increases. the capacity of the system. It is to be noted that this system will operate to supply gas without the use of the auxiliary vaporizer even if the earth is cooled to a relatively low temperature. As long as any part of the vaporizing section of the system is above the initial boiling point of the liquid, gas willbe generated by the vaporization of a part Since the temperature o! the liquid. The unvaporized portion of the liquid will accumulate in the carbureting tank until subsequently vaporized. v

I claim: I

1. A liquefied gas vaporizing anddispensing system comprising in combination a container for the liquefied gas disposed above the ground, conduit means for withdrawal oi said liquid from said container comprising in the direction of.

withdrawal a pressure reducer for vaporizing and thereby cooling at least a portion or said liquid by pressure reduction, and a heat exchange means disposed above ground for vaporizing at least a portion of any remaining liquid by reheating to at least substantially the tempera ture of said container, a carburetor chamber disposed under the ground below the frost line in heat exchange relation with the ground, said conduit means from said heat exchange means 2. The combination of claim 1 in which a gas pressure regulator is disposed in the dispensing conduit to control the maximum pressure oi the gas being dispensed therethrough.

' 3. The combination of claim 1 in which the I heat exchange means disposed above ground is an atmospheric heat exchanger in the same atmosphere as the container.

4. The combination of claim 1 in which the I heat exchan e means disposed above ground is a furnace fired by gas from the dispensing conduit.

ARTHUR N. KERR. 

